Why we feel so bad the next day...

Congeners are toxic byproducts of distillation and fermentation. These chemical impurities are the substances responsible for giving each drink its individual taste, color and aroma.Congeners do not cause drunkenness, but do add to your hangover.

Some spirits are higher in congeners than others. Red wine, brandies, and whiskies are usually higher than other types of alcohol. Each spirit has its own identifying congeners which give it a unique flavor. The liver must process these, so it is best to avoid mixing your spirits.

The distillation process has a direct relation to the amount of congeners found in your spirits. The pot still is generally used to produce high end brandies, malt whiskies, and dark rums for example. These are more flavorful as they contain more congeners. The Coffey still, developed in the early 19th century, is a continuous column still where most congeners are removed and almost pure ethanol is produced. This is also known as a neutral spirit. To reduce or eliminate remaining impurities this distilled alcohol can now be diluted, filtered through charcoal, and then rectified (redistilled). Many distillers now combine both methods of distillation to give the end product the best of both worlds.

In 1999, Jeffrey Wiese of the Veterans Affairs Medical Center in San Francisco and colleagues from the University of California, San Francisco, began investigating a series of studies on hangovers that began in 1965. In one experimental setting, 33 percent of patients who consumed 1.5 g/kg of body weight of bourbon experienced a severe hangover. However, only 3 percent of those who drank the same amount of vodka experienced the same.*

A rule of thumb is the clearer your spirit, the fewer congeners it has, and the less severe the hangover. Highly filtered vodkas generally contain the smallest amount. Another tip is in the price of your spirits. The cheaper it is, the less it has been processed to remove the impurities.

*Source: The Annals of Internal Medicine, June 6, 2000